1. Technical Field
The present invention relates to an automatic adjustment type method and system for detecting tactile information in which sensitivity can be automatically adjusted in accordance with outputs of strain gauges constituting sensor elements adhered to measurement locations.
2. Related Art
Human skin has various types of touch receptors that enable it to distinguish touches ranging from light touches to impact forces. There are approximately 1500 Meissner's tactile corpuscles and 750 Merkel's tactile disks per square centimeter in the upper part of the skin of the fingertip, and some 75 Pacinian corpuscles and Ruffini endorgans per square centimeter. These four types of touch receptors, with their different time and spatial responses, provide a broad measuring range.
In an environment in which people and robots coexist, it is considered that the robots would have to be equipped with touch sensors that continuously measure over an appropriate range. For example, high-sensitivity touch sensors may be required if robotic fingertips are used to carry out delicate tasks. On the other hand, to avoid dangers, sensors may be required that can also measure large impact forces.
Research into robotic touch sensors started around 1960 with the work of H. Erunst and others. Since that time, numerous touch sensors have been proposed from various perspectives, and have been improved with respect to, for example, sensitivity, resolution, linearity, reduced-wiring configurations, mounting, and so forth.
A method that is widely used in the prior art is to arrange touch sensors in an (M×N) matrix and sequentially switch from sensor to sensor to measure tactile information at each sensor measurement point where each touch sensor is arranged. A drawback of these touch sensors is that it requires many wires to read the information at the measurement points. To reduce the number of wires, Shinoda and others, for example, have proposed new types of wireless sensing configurations that use coils for electric power transmission and sensing. Comprising numerous resonance circuits set in a flexible material, these sensors can distinguish which portion is touched.
A problem with conventional touch sensors is that sensor resolution is degraded by an input of a strong signal exceeding a prescribed level, which causes saturation, or when a touch force is a very small one. To overcome this, the touch sensors require automatic gain control (hereinbelow, AGC) to automatically adjust a gain to a level appropriate to a sensor input.
Also, with respect to using touch sensors over a large area, since the touch force input to sensor elements is not uniform, there may be parts that become saturated, degrading the resolution. To prevent this, it should be made possible to individually adjust the sensor element gain at each measurement point. Also, when wired touch sensors are used, it should be made possible to reduce the number of wires that run between the measurement point sensor elements and a controller used to detect the tactile information at each measurement point, from outputs of the sensor elements.